Add solver abstract base class, and sub-classes for existing Solver c…

…lass.

Begin re-writing solver compile. Issue #72 and #57.
Collection Execution is a separate module.

python/mmSolver/_api/action.py

@@ -0,0 +1,28 @@
+# Copyright (C) 2019 David Cattermole.
+#
+# This file is part of mmSolver.
+#
+# mmSolver is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# mmSolver is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with mmSolver.  If not, see <https://www.gnu.org/licenses/>.
+#
+"""
+Actions - a wrapper tuple for a callable function with positional and keyword arguments.
+"""
+
+import collections
+
+
+Action = collections.namedtuple(
+    'Action',
+    ('func', 'args', 'kwargs')
+)